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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1678 Datasheet

1-Cell to 2-Cell / Low-Noise / High-Efficiency / Step-Up DC-DC Converter

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19-1381; Rev 0; 7/98
EVAALVUAAILTAIOBNLEKIT
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
General Description
The MAX1678 is a high-efficiency, low-voltage, syn-
chronous-rectified, step-up DC-DC converter intended
for use in devices powered by 1 to 3-cell alkaline,
NiMH, or NiCd batteries or a 1-cell lithium battery. It
guarantees a 0.87V start-up voltage and features a low
37µA quiescent supply current.
The device includes a 1, N-channel MOSFET power
switch, a synchronous rectifier that acts as the catch
diode, a reference, pulse-frequency-modulation (PFM)
control circuitry, and circuitry to reduce inductor ring-
ing—all in an ultra-small, 1.1mm-high µMAX package.
The output voltage is preset to 3.3V or can be adjusted
from +2V to +5.5V using only two resistors. Efficiencies
up to 90% are achieved for loads up to 50mA. The
device also features an independent undervoltage
comparator (PFI/PFO) and a logic-controlled 2µA shut-
down mode.
Features
o 0.87V Guaranteed Start-Up
o Up to 90% Efficiency
o Built-In Synchronous Rectifier (no external diode)
o Ultra-Small µMAX Package, 1.1mm High
o 37µA Quiescent Current (85µA from 1.5V battery)
o 2µA Logic-Controlled Shutdown
o Power-Fail Detector
o Dual Mode™ Output: Fixed 3.3V
Adjustable 2V to 5.5V
o 45mA Output Current at 3.3V for 1-Cell Input
o 90mA Output Current at 3.3V for 2-Cell Input
o Inductor-Damping Switch Suppresses EMI
Applications
Pagers
Remote Controls
Pointing Devices
Personal Medical Monitors
Single-Cell Battery-Powered Devices
Ordering Information
PART
MAX1678EUA
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 µMAX
Note: To order these devices shipped in tape-and-reel, add a -T
to the part number.
Typical Operating Circuit
Pin Configuration
INPUT
0.87V TO VOUT
ON
OFF
LOW-BATTERY
DETECTOR INPUT
LX OUT
MAX1678
BATT
SHDN
PFI
GND
PFO
FB
OUTPUT
3.3V
LOW-BATTERY
DETECTOR OUTPUT
TOP VIEW
BATT 1
PFI 2
PFO 3
SHDN 4
MAX1678
µMAX
8 OUT
7 LX
6 GND
5 FB
Dual Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.


Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1678 Datasheet

1-Cell to 2-Cell / Low-Noise / High-Efficiency / Step-Up DC-DC Converter

No Preview Available !

1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
ABSOLUTE MAXIMUM RATINGS
BATT, OUT,LX, SHDN to GND ..............................-0.3V to +6.0V
OUT, LX Current.......................................................................1A
FB, PFI, PFO to GND ................................-0.3V to (VOUT + 0.3V)
Reverse Battery Current (TA = +25°C) (Note 1) ...............220mA
Continuous Power Dissipation (TA = +70°C)
µMAX (derate 4.1mW/°C above +70°C) .......................330mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1: The reverse battery current is measured from the Typical Operating Circuit’s input terminal to GND when the battery is con-
nected backward. A reverse current of 220mA will not exceed package dissipation limits but, if left for an extended time
(more than 10 minutes), may degrade performance.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VBATT = VSHDN = 1.3V, ILOAD = 0, FB = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Minimum Operating Input
Voltage
VBATT(MIN)
0.7 V
Maximum Operating Input
Voltage
VBATT(MAX)
5.5 V
Start-Up Voltage (Note 2)
Start-Up Voltage Tempco
RL = 3k, TA = +25°C
0.87
-2
V
mV/°C
Output Voltage (Fixed Mode)
Output Voltage Range
(Adjustable Mode)
VOUT
VFB < 0.1V
External feedback
3.16 3.3 3.44
2.0 5.5
V
V
FB Set Voltage
N-Channel On-Resistance
P-Channel On-Resistance
P-Channel Catch Diode Voltage
Maximum Peak LX Current
On-Time Constant
Quiescent Current into OUT
Quiescent Current into BATT
Shutdown Current into OUT
Shutdown Current into BATT
Efficiency
FB Input Current
PFI Trip Voltage
PFI Input Current
PFO Low Output Voltage
PFO Leakage Current
SHDN Input Low Voltage
SHDN Input High Voltage
SHDN Input Current
VFB
ILX(MAX)
K
IQ,OUT
IQ,BATT
ISHDN,OUT
ISHDN,BATT
η
VIL,PFI
VOL
VIL
VIH
External feedback
VOUT = 3.3V
VOUT = 3.3V
IDIODE = 100mA, P-channel switch off
0.9V < VBATT < 3.3V (tON = K / VBATT)
VOUT = 3.5V
VOUT = 3.5V
VBATT = 1V
ILOAD = 20mA, VBATT = 2.5V (Figure 7)
VFB = 1.3V
Falling PFI hysteresis 2%
VPFI = 650mV
VPFI = 0, VOUT = 3.3V, ISINK = 1mA
VPFI = 650mV, VPFO = 6V
SHDN = GND or BATT
1.19 1.23 1.26
1 1.5
1.5 2.2
0.8
550
5.60 8 11.2
37 65
48
0.1 1
2 3.5
90
0.1 10
590 614 632
0.1 10
0.04 0.4
0.01 1
0.8 x VBATT
0.2 x VBATT
0.1 10
V
V
mA
V-µs
µA
µA
µA
µA
%
nA
mV
nA
V
µA
V
V
nA
2 _______________________________________________________________________________________


Part Number MAX1678
Description 1-Cell to 2-Cell / Low-Noise / High-Efficiency / Step-Up DC-DC Converter
Maker Maxim
Total Page 12 Pages
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